Quite often one leads to the other, and I always had a lot of compassion for those who could handle the withdrawal from alcohol, but couldn't handle giving up the other drugs at the same time. They led a miserable life.
Well --- I know I have far more compassion for the drug users than for the drug dealers. I doubt anyone sits down and decides to become addicted, addiction can take place quickly or over time ---- and it seems to me that addict might be trying to self-medicate for some kind of depression or emotional pain --- the traffickers only motivation is greed. So as much as the narcotrafficking Mexican government tries to blame the users in the USA entirely for this problem --- it's a weak argument. They chose greed and now have to live with the consequences.
First time coke users usually can't see that it does anything. It often takes a half dozen times before people actually learn to distinguish the high.